Biological H2S production is a complex process and the rate of this process may be subject to many disturbances including chemical feed quality, sulphur particle size, pH, conductivity, and temperature. At the same time, the capacity of an H2S supply system to respond rapidly to changes and fluctuations in the H2S demand by the end user of the H2S, for example, an industrial process, is important to a successful integration of the biological H2S generation process into industrial applications.
The traditional processes for the production of hydrogen sulphide from the bacterial reduction of a mixture of a liquid and elemental sulfur with an electron donor can be difficult to control and prone to swings in production rates. These control difficulties can make the processes unsuitable for commercial application, where a continuous, reliable source of H2S is desired. Biebl and Pfenning (1978) describe culture types and culture media for the reduction of elemental sulfur using acetate, among other compounds. Buisman (1989) describes optimal pH and temperature regimes for such cultures, as well as investigates substrate and product limitations. U.S. Pat. No. 6,852,305 describes a process for H2S production using elemental sulfur and an electron donor, such as hydrogen gas, carbon monoxide or organic compounds. The bacteria may be Desulforomanas sp (mesophilic), Desulfotomaculum KT7 (thermophilic), etc. The liquid/sulfur mixture is at a pH ranging from 5 to 9, and the liquid/sulfur mixture contacts the bacteria at a hydraulic retention time of at least 1 day. The hydrogen sulphide is stripped from the liquid medium to produce a gas containing at least 1 volume percent hydrogen sulphide. In Huisman (2006), the reaction of sulfide with elemental sulphur to form polysulphides, which are then used by bacteria as an electron acceptor, is described, along with early attempts to commercialize the H2S generator process for the treatment of acid rock drainage (ARD).